array_queue: add core implementation

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Adds a no_std, no_alloc implementation of the ArrayQueue.

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After porting the ArrayQueue implementation to heapless, I thought upstream might also want a no-alloc implementation.

Most of the diffs are code motion of moving the existing alloc implementation into submodules (for src + tests). The rest is the core implementation, which is mostly a copy of the original, with some tweaks to remove the alloc dependency.